Infancy Biosocial Development: Chapter 5 Human Development & Learning

Hail Mary, full of grace! The Lord is with thee; blessed art thou among women, and blessed is the fruit of thy womb, Jesus. Holy Mary, Mother of God, pray for us sinners now and at the hour of our death. Amen.

The Infant 0-2 What is an infant like at birth? At 1 week? At around 1 year? At 2 years? These are all videos of girls. We need to remember that individuals vary and that girls and boys, on average, develop differently and at different rates. For example, females tend to be more verbal than males, and we see this difference very early.

Tracking Development Percentile ranks: A point on a ranking scale of 0 to 100, with 50th percentile as midpoint. Allows comparisons of an individual infant to group norms A sudden drop in percentile rank might indicate a developmental problem.

Height & Weight Average N. American newborn Length: 20 inches (95%: 18-22) + 1 in/month during first year Weight: 7.5 lbs (95%: 5.5-10) + 5-6 oz/week in first month x 2 in 4 months x 3 in 12 month By 2 years 26-32 lbs (1/5 adult weight) and 32-35 in. (1/2 adult height)

Infant Sleep Typical newborns sleep around 16-17 hrs/day By 1 month, they sleep longer at night. By 4 months, closer to adult-like sleeping patterns. REM sleep: Infants spend much longer than adults in REM sleep. Why? By about 3 months, all stages of sleep observed

Infant Sleep (cont.) Infants gradually adjust to the family’s sleep schedule. 80% of 1 year olds sleep “through the night” Sleep cycles are influenced by brain maturation, diet, child-rearing practices, and birth order

Sudden Infant Death Syndrome (SIDS) Highest “cause” of infant death in U.S. Higher risks: low birth weight, exposure to secondhand smoke, soft bedding. Less likely with pacifier. American Academy of Pediatrics (AAP) suggest that infants sleep on their backs. Lying prone Impairs arousal from sleep, restricts swallowing. Around 3000 anually. 1-3 months high risk

Co-Sleeping Some families practice “co-sleeping,” in which the family shares a bed. Why might a family do this? Do you think it could benefit or harm an infant?

Research on Co-Sleeping CULTURE influences the decision (it is more common in Eastern culture) It is not harmful to an infant, under normal circumstances (e.g., if adult is not drunk) It may increase dependence on parents

Head-sparing Most early weight is fat (aka “baby fat”) Head-sparing: in cases of inadequate nutrition, the brain keeps growing

Brain Growth Newborn: About ¼ of its adult weight. By age 2: About 75% of adult weight. Neurons: Nerve cell that handles information processing (IP) Axons (sends) Dendrites (receives) Myelin sheath (speeds communication)

Brain Structures Brain stem: controls automatic responses like heartbeat, breathing, temperature, arousal. Midbrain: emotions, memory, integration Cortex: higher level functioning Sensory cortices Fusiform Face Area…so cool. Own-race effect

Neuronal changes in infancy Most neurons are created before birth Peak production: 250,000 new brain cells/minute in mid-pregnancy!!! Increased connectivity Transient Exuberance (aka “blooming and pruning”) We make nearly twice the amount of connections we will ever use. As many as 15,000 new connections per neuron and 100 trillion synapses by age 2! Myelination begins prenatally and continues through adolescence. Makes information processing faster Visual myelination in first 6 months Auditory myelination by 4 or 5 4 months: Visual overproduction, gradual retraction through preschool. Prefrontal cortex: 1 year to mid-late adolescence

The brain and early experience Infants are born with a “toolbox,” not a complete set of skills. Before birth, genes direct basic wiring. After birth, the environment helps shape the brain. What are the implications of this? The growing brain is incredibly flexible and resilient.

The Developing Cortex

Why are neural connections so important? A certain level of neural connections indicate healthy brain development. Lack of connections may result from child abuse or neglect early in life, and can have lasting consequences. Example: Infants in orphanages

Implications for Caregivers Is it possible to overstimulate an infant? Yes. The key is to follow the infant’s lead Self-righting: an infant’s inborn drive to use whatever experiences available to develop the brain.

Infant Senses All five senses function at birth Vision, hearing, taste, touch, smell Perception (the brain’s processing of the sensation) develops over time.

Infant Senses (cont.) Hearing: is well developed at birth Infants respond to sudden noises, human voice, phonemes of language Vision: is the least mature sense at birth Bionocular vision develops around 14 weeks “Adult” vision (20/20) by one year

Infant Senses (cont.) Taste, touch, smell function well at birth All: CINDY CHARLES / PHOTOEDIT, INC.

Motor Skills Motor skills develop according to two principles: Cephalocaudal: growth proceeds from head-to-toe (e.g., head lift before sit, stand, walk) Proximal-distal: growth proceeds from torso outward (e.g., sucking before kicking)

Motor Skills (cont.) Reflexes account for the first motor skills. Survival reflexes include sucking, breathing, body temperature. Other reflexes include the Babinski, Moro, and stepping reflexes.

Infant Reflexes ASTIER / BSIP / SCIENCE SOURCE / PHOTO RESEARCHERS, INC. JENNY WOODCOCK; REFLECTIONS PHOTOLIBRARY / CORBIS PETIT FORMAT / PHOTO RESEARCHERS, INC.

Motor Skills (cont.) Gross motor skills involve large muscle movements. Examples: crawling, sitting, walking Walking typically occurs around 12 months, with great variability across infants. Walking requires muscle strength, brain maturation, and practice.

Motor Skills (cont.) Fine motor skills involve small muscle movements. Examples: learning to grasp, shake, pull an object, hold a spoon, write, draw, etc. Motor skills are influenced by genes, culture, and patterns of infant care.

Public Health Measures Infant survival rates have increased significantly in the past century, due to better nutrition, cleaner water, and immunization. Although not without controversy, immunization has been hailed as a major achievement (e.g., significantly reducing polio, small pox, measles).